SUNRPC: Allow caller to specify the transport to use

This is needed in order to allow the NFSv4.1 backchannel and
BIND_CONN_TO_SESSION function to work.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index 73ad57a..fcfd48d 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -909,6 +909,8 @@
 	/* Initialize workqueue for async tasks */
 	task->tk_workqueue = task_setup_data->workqueue;
 
+	task->tk_xprt = xprt_get(task_setup_data->rpc_xprt);
+
 	if (task->tk_ops->rpc_call_prepare != NULL)
 		task->tk_action = rpc_prepare_task;